Java constructor initialize oder

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// housekeeping/OrderOfInitialization.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// Demonstrates initialization order

// When the constructor is called to create a
// Window object, you'll see a message:
class Window {
  Window(int marker) {
    System.out.println("Window(" + marker + ")");
  }
}

class House {
  Window w1 = new Window(1); // Before constructor

  House() {
    // Show that we're in the constructor:
    System.out.println("House()");
    w3 = new Window(33); // Reinitialize w3
  }

  Window w2 = new Window(2); // After constructor

  void f() {
    System.out.println("f()");
  }

  Window w3 = new Window(3); // At end
}

public class OrderOfInitialization {
  public static void main(String[] args) {
    House h = new House();
    h.f(); // Shows that construction is done
  }
}
/* Output:
Window(1)
Window(2)
Window(3)

House()
Window(33)
f()
*/

ps: blank lines in comments are used to highlight constructor initialize oder.

When add a constructor with one int parameter.

// housekeeping/OrderOfInitialization.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// Demonstrates initialization order

// When the constructor is called to create a
// Window object, you'll see a message:
class Window {
  Window(int marker) {
    System.out.println("Window(" + marker + ")");
  }
}

class House {
  Window w1 = new Window(1); // Before constructor

  House() {
    // Show that we're in the constructor:
    System.out.println("House()");
    w3 = new Window(33); // Reinitialize w3
  }

  House(int i) {
    System.out.println("args i:" + i);
  }

  Window w2 = new Window(2); // After constructor

  void f() {
    System.out.println("f()");
  }

  Window w3 = new Window(3); // At end
}

public class OrderOfInitialization {
  public static void main(String[] args) {
    House h = new House();
    h.f(); // Shows that construction is done
    new House(1);
  }
}
/* Output:
Window(1)
Window(2)
Window(3)

House()
Window(33)
f()

Window(1)
Window(2)
Window(3)
args i:1
*/

change house(int i) location did not change the output.

references:

1. On Java 8 - Bruce Eckel

2. https://github.com/wangbingfeng/OnJava8-Examples/blob/master/housekeeping/OrderOfInitialization.java

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转载自blog.csdn.net/wangbingfengf98/article/details/85235096